1. Field of the Invention
The present invention relates to the fixed bed catalytic hydrogenation of 4-hydroxybutyraldehyde to 1,4-butanediol and/or to the fixed bed catalytic hydrogenation of 2-methyl 3-hydroxypropionaldehyde to 2-methyl 1,3-propandiol.
2. Description of the Prior Art
A commercial route to 1,4-butanediol (BDO) comprises the carbonylation of allyl alcohol to 4-hydroxybutyraldehyde (HBA) and the hydrogenation of HBA to BDO. Patents which are illustrative of this technology include U.S. Pat. No. 6,225,509 and the patents cited therein. Generally, in the allyl alcohol carbonylation some 2-methyl 3-hydroxypropionaldehyde (HMPA) is formed and this can subsequently be hydrogenated to 2-methyl 1,3 propanediol (MPD).
Problems are encountered in each of the hydrogenation steps especially where fixed bed hydrogenation procedures are used. The fixed bed catalyst tends to deactivate and physically deteriorate with time and as a result slurry hydrogenation procedures have been the norm. For economic reasons the development of successful fixed catalyst bed procedures would be distinctly advantageous.